Hg(II) Coordination Polymers Based on N,N '-bis(pyridine-4-yl)formamidine

作者：Hsu Wayne; Yang Xiang Kai; Chhetri Pradhumna Mahat; Chen Jhy Der^*

来源：Polymers, 2016, 8(4): 137.

DOI：10.3390/polym8040137

• coordination polymer
• mercury
• formamidine

Reactions of N,N'-bis(pyridine-4-yl)formamidine (4-Hpyf) with HgX2 (X = Cl, Br, and I) afforded the formamidinate complex {[Hg(4-pyf)(2)]center dot(THF)}(n), 1, and the formamidine complexes {[HgX2(4-Hpyf)]center dot(MeCN)}(n) (X = Br, 2; I, 3), which have been structurally characterized by X-ray crystallography. Complex 1 is a 2D layer with the {4(4).6(2)}-sql topology and complexes 2 and 3 are helical chains. While the helical chains of 2 are linked through N-H center dot center dot center dot Br hydrogen bonds, those of 3 are linked through self-complementary double N-H center dot center dot center dot N hydrogen bonds, resulting in 2D supramolecular structures. The 4-pyf-ligands of 1 coordinate to the Hg(II) ions through one pyridyl and one adjacent amine nitrogen atoms and the 4-Hpyf ligands of 2 and 3 coordinate to the Hg(II) ions through two pyridyl nitrogen atoms, resulting in new bidentate binding modes. Complexes 1-3 provide a unique opportunity to envisage the effect of the halide anions of the starting Hg(II) salts on folding and unfolding the Hg(II) coordination polymers. Density function theory (DFT) calculation indicates that the emission of 1 is due to intraligand pi-pi* charge transfer between two different 4-pyf-ligands, whereas those of 2 and 3 can be ascribed to the charge transfer from non-bonding p-type orbitals of the halide anions to pi* orbitals of the 4-pyf-ligands (n ->pi*). The gas sorption properties of the desolvated product of 1 are compared with the Cu analogues to show that the nature of the counteranion and the solvent-accessible volume are important in determining their adsorption capability.

• 出版日期2016-4